As a natural result of economical globalization, the range of human activity is getting larger and larger, and the demand for international roaming communication is increasing accordingly. Since a prepaid subscriber subscribes to a Service Control Point (SCP) in his/her home country, the subscriber may not be triggered to his/her subscribed SCP in an international roaming condition when he/she roams out of his home country to other countries, which leads to a failure of the international roaming calling service.
A method generally taken in the related art as a solution to the above problem comprises: a prepaid calling subscriber initiating a call; prefixing the called number with an Unstructured Supplementary Service Data (USSD); routing the call to the subscribed SCP of the calling subscriber; triggering the SCP to initiate a two-segment call to the calling subscriber and to the called subscriber, respectively; and joining the two-segment call to realize the calling call of the prepaid subscriber in the roamed country.
The inventor found out in implementing the invention that in the related art, when a prepaid subscriber initiates a call as the calling party in the roamed country, he/she needs to dial the USSD prefix before the called number in order to make a call, and the numbers in the original contact book could not be used for calling unless they are supplemented with the USSD prefix, which results in complex and inconvenient operations.